aio: keep io_event in aio_kiocb

commit a9339b7855094ba11a97e8822ae038135e879e79 upstream.

We want to separate forming the resulting io_event from putting it
into the ring buffer.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>